Two men suffered serious injuries in an attack at Tramlines music festival last month.
Police have issued an appeal for witnesses after the men were assaulted two at the Arundel Gate taxi rank in Sheffield.
At around 4am on Saturday July 25, it is believed that the two victims were stood waiting for a taxi at the taxi rank near to Tank nightclub in Arundel Gate.
The two men, aged 24 and 29, were approached by an unknown man who assaulted them.
The 24-year-old was knocked unconscious and required surgery for his injuries. The 29-year-old was also knocked unconscious and suffered facial injuries.
The suspect is described as being a white man, around 6ft tall, of heavy build. He is described as having corn rows in his hair and was wearing a light grey t-shirt with a pattern on the rear.
Police are asking witnesses to call 101 quoting incident number 555 of 28 July 2015.